Add api response for the httpcode specified by response status

[rudolfgrauberger]

Describe the problem

If you specify the default controller endpoint HTTP status code via @ResponseStatus and then add the special/error cases via @ApiResponse, the http code you specified with @ResponseStatus will not be listed as a possible response.

To Reproduce

What version of spring-boot you are using?

1.6.9

What modules and versions of springdoc-openapi are you using?

springdoc-openapi-ui

What is the actual and the expected result using OpenAPI Description (yml or json)?

actual

{
  "openapi": "3.0.1",
  "info": { "title": "OpenAPI definition", "version": "v0" },
  "servers": [
    { "url": "http://localhost:8080", "description": "Generated server url" }
  ],
  "paths": {
    "/withResponseStatus": {
      "get": {
        "tags": ["hello-controller"],
        "description": "200 defined by @ResponseStatus",
        "operationId": "withResponseStatus",
        "responses": {
          "422": {
            "description": "Test",
            "content": {
              "application/json": { "schema": { "type": "string" } }
            }
          },
          "409": {
            "description": "Test 2",
            "content": {
              "application/json": { "schema": { "type": "string" } }
            }
          }
        }
      }
    }
  },
  "components": {}
}

expected

{
  "openapi": "3.0.1",
  "info": { "title": "OpenAPI definition", "version": "v0" },
  "servers": [
    { "url": "http://localhost:8080", "description": "Generated server url" }
  ],
  "paths": {
    "/withResponseStatus": {
      "get": {
        "tags": ["hello-controller"],
        "description": "200 defined by @ResponseStatus",
        "operationId": "withResponseStatus",
        "responses": {
          "422": {
            "description": "Test",
            "content": {
              "application/json": { "schema": { "type": "string" } }
            }
          },
          "409": {
            "description": "Test 2",
            "content": {
              "application/json": { "schema": { "type": "string" } }
            }
          },
          "200": {
            "description": "OK",
            "content": {
              "application/json": { "schema": { "type": "string" } }
            }
          }
        }
      }
    }
  },
  "components": {}
}

Provide with a sample code (HelloController) or Test that reproduces the problem

	@Operation(description = "200 defined by @ResponseStatus",
		responses = {
			@ApiResponse(responseCode = "422", description = "Test")
	})
	@ApiResponses({
			@ApiResponse(responseCode = "409", description = "Test 2")
	})
	@GetMapping(value = "/withResponseStatus", produces = MediaType.APPLICATION_JSON_VALUE)
	@ResponseStatus(value = HttpStatus.OK)
	public ResponseEntity<String> withResponseStatus() {
		return ResponseEntity.ok("hello");
	}

Expected behavior

According to the documentation for @ResponseStatus this annotation specifies which code should be returned.

With this, in my opinion, the code specified in @ResponseStatus should also be specified as a possible response. Of course only if it is not overridden by an explicit @ApiResponse documentation.

[bnasslahsen]

Thanks @rudolfgrauberger for your contribution to the project.